feat(dapps): show the bundled DApps catalog until one can be fetched

The DApps catalog lived only in memory and every read waited on first(), so
with the catalog URL unreachable the DApps screen waited forever.

feature-dapp-impl now bundles dapps_full.json at build time. On the first
sync the repository tries the network once and, if that fails, publishes the
bundled catalog so every read returns; the fetched catalog replaces it as
soon as it arrives.

The download task moves to scripts/bundled-config.gradle and serves both
the chain list and the DApps catalog. runtime and feature-dapp-impl unit
tests return defaults for android.util.Log, which the fallback calls.

scripts/bundled-config.gradle

@@ -0,0 +1,44 @@
+// Config files the APK is built with, so a first install can open when none can be fetched
+// (GitHub blocked, offline). Each is the live file at build time, fetched from GitHub or its jsDelivr
+// mirror, checked by the caller's `isUsable`, and placed in the module's assets under `assetPath`.
+//
+//   apply from: '../scripts/bundled-config.gradle'
+//   bundleConfigAsset("bundleChainsConfig", chainsUrl, "bundled-config/chains.json") { it instanceof List && !it.isEmpty() }
+
+ext.bundleConfigAsset = { String taskName, String url, String assetPath, Closure isUsable ->
+    def outputDir = "$buildDir/generated/bundledConfig"
+    def target = file("$outputDir/$assetPath")
+
+    def task = tasks.register(taskName) {
+        outputs.file(target)
+        outputs.upToDateWhen { false }
+
+        doLast {
+            def sources = [
+                url,
+                url.replaceFirst('^https://raw\\.githubusercontent\\.com/([^/]+)/([^/]+)/([^/]+)/', 'https://cdn.jsdelivr.net/gh/$1/$2@$3/')
+            ]
+            def bytes = null
+            for (source in sources) {
+                try {
+                    bytes = new URL(source).getBytes(connectTimeout: 20_000, readTimeout: 60_000)
+                    break
+                } catch (IOException e) {
+                    logger.warn("$taskName: $source failed: $e")
+                }
+            }
+            if (bytes == null) throw new GradleException("$taskName: no source answered for $url")
+
+            def parsed = new groovy.json.JsonSlurper().parse(bytes)
+            if (!isUsable(parsed)) throw new GradleException("$taskName: $url is not a usable config file")
+
+            target.parentFile.mkdirs()
+            target.bytes = bytes
+            def sha256 = java.security.MessageDigest.getInstance("SHA-256").digest(bytes).encodeHex().toString()
+            logger.lifecycle("$taskName: $assetPath ${bytes.length} bytes, sha256 $sha256")
+        }
+    }
+
+    android.sourceSets.main.assets.srcDir(outputDir)
+    preBuild.dependsOn(task)
+}